Daylight-driven rechargeable antibacterial and antiviral nanofibrous membranes for bioprotective applications

Si, Yang; Zhang, Zheng; Wu, Wanrong; Fu, Qiuxia; Huang, Kang; Nitin, Nitin; Ding, Bin; Sun, Gang

We further compared the photo-induced structural reorganization of RNMs by typical absorption intensity change related to DPM (262 nm) and LAT (420 nm) structures. As shown in Fig. 3F , the BDCA-RNM exhibited negligible DPM formation while having the maximum LAT transition ability, indicating that the activity-stored structure was able to recover with rare functional decaying. To quantify the ROS rechargeable capability, we first charged the relevant RNMs by 1 hour of daylight irradiation and then measured the releasing activity under dark conditions in terms of the amount of OH• and H 2 O 2 . As shown in Fig. 3 (G and H) , in contrast to the gradual ROS generation in irradiation tests, the RNMs rapidly released more than 90% of ROS in the first 5 min, and after that, the releasing ability shows a saturation region with ROS amount increasing slowly. As expected, the BDCA-RNM exhibited the highest recharging capacity, with OH• and H 2 O 2 releasing amounts of 2332 and 670 mg g −1 by 1 hour of daylight charging, corresponding to the charging rates of 38.86 and 11.16 mg g −1 min −1 , respectively, which means that the light energy was largely used with more than 70% conversion efficiency compared to the irradiation tests. Moreover, the recharging cyclic test of BDCA-RNM was performed as displayed in Fig. 3I . For each cycle, the BDCA-RNM samples were first irradiated for 1 hour and were fully quenched with an excess amount of a thiosulfate solution. No significant decrease in the recharging capacity was observed for BDCA-RNM after seven cyclic tests; they retained more than 75% of the original charging amount of OH• and H 2 O 2 . The nanofibrous architecture was also well maintained during the seven cycles of recharging, as demonstrated in Fig. 3J . The slight decrease of the capacity could be attributed to the accumulative consumption of the nonrenewable tertiary hydrogen in the PVE-co-PE nanofiber matrix (35, 42) . In addition, stability for long-time storage of the LAT structure is another practical concern for recharging performance. The decay of the LAT structure occurred notably on the existence of oxygen and reductive organic matter, which could lead to a quick release of ROS. Therefore, if the RNMs were stored under a dry and closed condition, then the absorption peak associated with the LAT structure should exhibit slow decays, which can be observed in Fig. 3K . A storage test over 30-day measurements revealed that the BDCA-RNM still retained more than 55% of the original LAT structure, highlighting the structural stability.